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The significant recovery of solutes from the PCT lumen to the interstitial space creates an osmotic gradient that promotes water recovery. As noted before, water moves through channels created by the aquaporin proteins. These proteins are found in all cells in varying amounts and help regulate water movement across membranes and through cells by creating a passageway across the hydrophobic lipid bilayer membrane. Changing the number of aquaporin proteins in membranes of the collecting ducts also helps to regulate the osmolarity of the blood. The movement of many positively charged ions also creates an electrochemical gradient. This charge promotes the movement of negative ions toward the interstitial spaces and the movement of positive ions toward the lumen.

Reabsorption of bicarbonate from the pct

This diagram shows the process of reabsorption of bicarbonate by the proximal collecting tubule.

Reabsorption and secretion in the loop of henle

The loop of Henle consists of two sections: thick and thin descending and thin and thick ascending sections. The loops of cortical nephrons do not extend into the renal medulla very far, if at all. Juxtamedullary nephrons have loops that extend variable distances, some very deep into the medulla. The descending and ascending portions of the loop are highly specialized to enable recovery of much of the Na + and water that were filtered by the glomerulus. As the forming urine moves through the loop, the osmolarity will change from isosmotic with blood (about 278–300 mOsmol/kg) to both a very hypertonic solution of about 1200 mOsmol/kg and a very hypotonic solution of about 100 mOsmol/kg. These changes are accomplished by osmosis in the descending limb and active transport in the ascending limb. Solutes and water recovered from these loops are returned to the circulation by way of the vasa recta.

Descending loop

The majority of the descending loop is comprised of simple squamous epithelial cells; to simplify the function of the loop, this discussion focuses on these cells. These membranes have permanent aquaporin channel proteins that allow unrestricted movement of water from the descending loop into the surrounding interstitium as osmolarity increases from about 300 mOsmol/kg to about 1200 mOsmol/kg. This increase results in reabsorption of up to 15 percent of the water entering the nephron. Modest amounts of urea, Na + , and other ions are also recovered here.

Most of the solutes that were filtered in the glomerulus have now been recovered along with a majority of water, about 82 percent. As the forming urine enters the ascending loop, major adjustments will be made to the concentration of solutes to create what you perceive as urine.

Ascending loop

The ascending loop is made of very short thin and longer thick portions. Once again, to simplify the function, this section only considers the thick portion. The thick portion is lined with simple cuboidal epithelium without a brush border. It is completely impermeable to water due to the absence of aquaporin proteins, but ions, mainly Na + , are actively pumped out of the loop by large quantities of the Na +/ K + ATPase pump. This has two significant effects: Removal of Na + while retaining water leads to a hypotonic filtrate by the time it reaches the DCT; pumping Na + into the interstitial space contributes to the hyperosmotic environment in the kidney medulla.

Questions & Answers

Minimum blood pressure
Hasnain Reply
120/80
AmirHameed
90/60
baila
120/80
Sri
were can anatomy work
capella Reply
in hospitality
Sri
what is normal flora
Cris Reply
it's one kind of bacteria
Tariq
the smallest blood vessel is capillary
Richard Reply
How does deoxygenated blood become oxygenated during blood circulation?
Richard
plzzz explain cardiac cycle
Piya Reply
what is anatomy
Gifty Reply
is the study of body structure
Amos
how types of tissue in body
mwiya
What are some of first questions are expected in anatomy and physiology course
Milner Reply
what is pacemaker
mekfira
its a device that is put into the heart to make sure it beats properly
Michelle
SA node produces impulse is called pacemaker
Piya
hi piya
Khubaib
hi Everyone
Hayat
hi everyone
Hong
hey
Edrick
hello
Damien
what's up
Damien
hlo
Lost
hi
Bok
hello
James
hi
IDDRISU
which of the following is the epithelial tissue that lines the interior of blood vessels?
Firomsa Reply
endothelial tissues
Osaki
Endothelial tissue
mabast
why are the questions only 3
Chisom Reply
you too can ask
Addo
what is the function of the skeletal system?
Cris
what is the treatment of herpes simplex virus?
riad Reply
the long bone with two primary center's of ossification for shaft is ________
Aarambam
medulla
Addo
good
Ravi
ha moj ha
Hani
doctor and nurse
Ravi
y 're the questions only 3
Chisom
women are much likely to be pregnant at which stage?
Fatoumatta Reply
There are only six days during any cycle when a woman can get pregnant - the five days leading up to ovulation and the 24 hours after ovulation. This is because sperm can live for up to 5 days in a woman's body, and the ovum lives for only 12-24 hours.
THE
right
Adil
does this apply to women close to menopose
Kuria
what's reason the reason for BP growing ?
Adil
when after they have intercourse
AJ
what is andropause
William Reply
It's the men version of menopause!
Catia
The testosterone levels decrease
Catia
what would happen if the sugar lever drops below the normal level
Marvin Reply
If our blood sugar drops below 70 mg/dL, we may have symptoms, such as feeling tired, weak, or shaky, become confused or drowsy or even lose consciousness and possibly die.
Dhanya
symptoms of hypoglycemia include: shakiness, dizziness, headache, confusion, rapid pulse rate, sweating, Hunger, etc.
EMERIBE
you right
Khubaib
You become dizzy and weak
evans
giddiness ND week
Sri
Is there any way to disable this chat feature or at least mute notifications? Also, does every textbook app from this creator have the chat function?
Atone Reply
I don't think you can disable chat and yes it is on every app
AJ
what is homeostasis
Nikky Reply
what is respiratory
Nikky
Respiratory is breathing
Atone
respiration is an exchange of gases (O2 & CO2) between the body and outside environment.
joey
homeostasis is internal balance.
Ali
Respiratory is system where the body takes in oxygen n releases carbondioxide
Hassan
respiratory system is a system where exhalation and inhalation takes place
Kom
1)inhalation: active diaphragm & external intercoastal muscles 2)exhalation: passive (allow muscle group to relax)
Shoukat
mantaince of body is called homeostasis
Komal
hi komal
Khubaib
how are you komal?
Khubaib
hi
Komal
hey nikki
Khubaib
hii komal
Rinku
where you from kamal?
Khubaib
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Rinku
oye rinku kya ha yahan kya kar rha ha
Khubaib
karachi
Komal
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Khubaib
never
Komal
0309
Khubaib
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Rinku
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Khubaib
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Rinku
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Khubaib
what is medical coding
Antony
waw komal
Rinku
yar rinku kahan se ho ap
Khubaib
I am from dausa,Rajasthan
Rinku
yar hum to pakistan se hain humy baat karny do
Khubaib
hoe r u alll
SARFARAJ
komal jha?
Khubaib
answer me please...What is basic concept or Acidosis?
Khalid
hiii komal
SARFARAJ
al hamd.o.lillah muslim
Khubaib
or aap
Khubaib
Allah ka shukr ha
SARFARAJ
aby tu b india chala ja un ko zarorat ha foji logon ki
Khubaib
beshak
Khubaib
myself Khalid Shabbir.Doctor of Anesthesia from PIMS Hospital.& belongs to Capital IslamAbad(Pakistan).
Khalid
yar sarfraz ap india se kab ay
Khubaib
tell me abt ethmoid bone
Sakshi
bro am all ready indian
SARFARAJ
okkk
SARFARAJ
hii sakshi how are you?
Khubaib
m gd..plz tell me the answer of it..
Sakshi
Face ki he ethmoid bone
Rakesh
ethmoid bone. Irregularly shaped bone anterior to the solenoid. Forms the roof of the nasal cavity, upper nasal septum, and part of the medial orbit walls.
LaKecia
Its unpaired bone of skull that saprate the nasal cavity from the brain it's located at the roof of the nose between the two orbits it's bone is one of the bones that make up the orbit of eye.
SARFARAJ
sphenoid I meant
LaKecia
wrist joint ka dusra name kya he
Rakesh
till me fast my ans
Rakesh
Also included in the ethmoid bone is the crista galli and the cribriform plates. The plates help form the roof of the nasal cavity and the floor of the anterior cranial fossa.
LaKecia
the outer most covering of the brain ( the dura mater) attached to the crista galli and helps secure the brain in the cranial cavity
LaKecia
Sakshi Mishra. I hope that helped!
LaKecia
thnks fo tellng😊
Sakshi
yup
Sakshi
yw
LaKecia
ye kya
Dr
hi
Dr
oh welcome sakshi
Khubaib
synovial joint will have present in wrist
sk
what's the smallest blood vessal in the body?
sk
respiration is the process of inspiration an expiration
Bel
first fall give me ans plz
sk
The protection of internal envirnment from the harm of external envirnmen is called as homeostasis.
Rana
skin
Sri
soma
Leanne
hello everyone?
George

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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